The World Anti-Doping Agency has been accused of having a “cowardly” attitude towards Russia and “betraying” clean athletes by the investigator who exposed Russian state-sponsored doping.

Jack Robertson, who was Wada’s chief investigator until January 2016, also said the decision by the organisation’s executive committee to reinstate the Russian Anti-Doping Agency in September had “tarnished Wada’s reputation forever”.

“What exactly did Russia do to deserve such leniency?” asked Robertson. “It never admitted guilt, never apologised, continually lied, withheld and destroyed evidence, threatened whistleblowers, made counteraccusations, was uncooperative in testing athletes, hacked into Wada’s computer databases and revealed sensitive athlete data, and continued to dope its athletes.

“Unfortunately, this most recent decision is in keeping with Wada’s culture in recent years as it responded to revelations about Russia’s state-sponsored doping program. As usual, Wada took the cowardly step of appearing to pass the buck to an expert committee that never had any real independence and predictably recommended that Russia be reinstated.”

Roberton’s intervention comes as Wada’s foundation board meets in Baku on Thursday to discuss the latest developments with Rusada, with delegates expected to hear whether the Russian government has agreed to grant an independent expert access to the Moscow anti-doping laboratory by the cut-off point of 31 December.

Wada insist that declaring Rusada compliant will give it a better chance of uncovering more evidence to prosecute Russian anti-doping cases. However Robertson, who also helped bring down Lance Armstrong and investigated Mexican drug cartels in his previous job with the US Drug Enforcement Agency, claimed that Wada had consistently not done enough to stand up to Russia, starting when he began investigations in 2015.

“[Wada president Sir Craig] Reedie’s reluctance was apparent throughout the investigation, like when he authored a consoling email to the Russian Sport Ministry, which later became public,” said Robertson. “That’s like the chief of police sending a private note to the target of an active investigation telling them he’s sorry, and not to worry. It is unconscionable, and would never be accepted outside of the pitiful state of affairs that is global anti-doping.”

“The current administration of Wada has fatally failed in its mission to safeguard the World Anti-Doping Code – the rules that govern clean sport – and in the process betrayed clean athletes,” he added. “The lone bright spot is that Wada’s unwillingness to protect clean sport is now so obvious that clean athletes are being pushed to take up arms, so to speak, and push for change.”